总结-HttpClient-RetryHandler重试
总结-HttpClient-RetryHandler重试
夜黑人模糊灬 发表于9个月前
总结-HttpClient-RetryHandler重试
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摘要: httpclient Retry

目前的项目接口都是http,因此在Java项目中使用apache httpclient进行数据传输、访问。

目前程序中涉及到需要callback操作,product需要被动的接收consume的处理状态,为了最大程度的能够callback成功因此consume在http调用出现问题(如:服务不可用、异常、超时)情况下需要进行重试(retry request),在这里我列举出我找到的retry方案,有些成功有些不成功。

我是用的httpclient版本是4.5.2。关于retry功能我在网上也找了不少的资料,但是都不是我对应的httpclient版本,大多是过时的。

在httpclient版本4.5.2提供了以下几种retry方案:

StandardHttpRequestRetryHandler

 

这种方案没有测试通过StandardHttpRequestRetryHandler实际上是DefaultHttpRequestRetryHandler的子类,这是官方提供的一个标准的retry方案,为了保证幂等性约定resetful接口必须是GET, HEAD, PUT, DELETE, OPTIONS, and TRACE中的一种,如下,是我定义的httpclient pool

public static CloseableHttpClient getHttpClient() {
    PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();
    cm.setMaxTotal(MAX_TOTAL);
    cm.setDefaultMaxPerRoute(MAX_PERROUTE);
    CloseableHttpClient httpClient = HttpClients
        .custom()
        .setRetryHandler(new StandardHttpRequestRetryHandler())
        .setConnectionManager(cm)
        .build();
    return httpClient;
}

如下是我的测试代码

@Test
public void test6(){
    HttpPost httpPost=new HttpPost("http://127.0.0.1:8080/testjobs1");
    try {
        rsp=httpClient.execute(httpPost);
        log.info(">> {}",rsp.getStatusLine().getStatusCode());
    } catch (Exception e) {
        log.error(e.getMessage(),e);
    }finally{
        HttpUtil.close(rsp);
    }
}

运行测试,当url错误、后台报错、后台超时等情况的时候不能进行retry,因此放弃了此方案。

DefaultHttpRequestRetryHandler

这种方案没有测试通过,和上面的StandardHttpRequestRetryHandler类似,它提供了一种默认的retry方案,并没有像StandardHttpRequestRetryHandler一样约定接口必须是冥等的,如下,是我定义的httpclient pool

public static CloseableHttpClient getHttpClient() {
    PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();
    cm.setMaxTotal(MAX_TOTAL);
    cm.setDefaultMaxPerRoute(MAX_PERROUTE);
    CloseableHttpClient httpClient = HttpClients
        .custom()
        .setRetryHandler(new DefaultHttpRequestRetryHandler())
        .setConnectionManager(cm)
        .build();
    return httpClient;
}

如下是我的测试代码

@Test
public void test6(){
    HttpPost httpPost=new HttpPost("http://127.0.0.1:8080/testjobs1");
    try {
        rsp=httpClient.execute(httpPost);
        log.info(">> {}",rsp.getStatusLine().getStatusCode());
    } catch (Exception e) {
        log.error(e.getMessage(),e);
    }finally{
        HttpUtil.close(rsp);
    }
}

依然没有达到希望的效果。

HttpRequestRetryHandler

可以实现,但是不够完美。在官方文档有这么一段,如下,

HttpRequestRetryHandler myRetryHandler = new HttpRequestRetryHandler() {
    public boolean retryRequest(
        IOException exception,
        int executionCount,
        HttpContext context) {
        if (executionCount >= 5) {
            // Do not retry if over max retry count
            return false;
        }
        if (exception instanceof InterruptedIOException) {
            // Timeout
            return false;
        }
        if (exception instanceof UnknownHostException) {
            // Unknown host
            return false;
        }
        if (exception instanceof ConnectTimeoutException) {
            // Connection refused
            return false;
        }
        if (exception instanceof SSLException) {
            // SSL handshake exception
            return false;
        }
        HttpClientContext clientContext = HttpClientContext.adapt(context);
        HttpRequest request = clientContext.getRequest();
        boolean idempotent = !(request instanceof HttpEntityEnclosingRequest);
        if (idempotent) {
            // Retry if the request is considered idempotent
            return true;
        }
        return false;
    }
};
CloseableHttpClient httpclient = HttpClients.custom().setRetryHandler(myRetryHandler).build();

自定义retry实现,这比较灵活,可以根据异常自定义retry机制以及重试次数,并且可以拿到返回信息,如下,是我定义的httpclient pool

public static CloseableHttpClient getHttpClient() {
    HttpRequestRetryHandler retryHandler = new HttpRequestRetryHandler() {
        public boolean retryRequest(
            IOException exception,
            int executionCount,
            HttpContext context) {
            if (executionCount >= 5) {
                // Do not retry if over max retry count
                return false;
            }
            if (exception instanceof InterruptedIOException) {
                // Timeout
                return false;
            }
            if (exception instanceof UnknownHostException) {
                // Unknown host
                return false;
            }
            if (exception instanceof ConnectTimeoutException) {
                // Connection refused
                return false;
            }
            if (exception instanceof SSLException) {
                // SSL handshake exception
                return false;
            }
            HttpClientContext clientContext = HttpClientContext.adapt(context);
            HttpRequest request = clientContext.getRequest();
            boolean idempotent = !(request instanceof HttpEntityEnclosingRequest);
            if (idempotent) {
                // Retry if the request is considered idempotent
                return true;
            }
            return false;
        }
    };
    PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();
    cm.setMaxTotal(MAX_TOTAL);
    cm.setDefaultMaxPerRoute(MAX_PERROUTE);
    CloseableHttpClient httpClient = HttpClients
        .custom()
        .setRetryHandler(retryHandler)
        .setConnectionManager(cm)
        .build();
    return httpClient;
}

如下是我的测试代码

@Test
public void test6(){
    HttpPost httpPost=new HttpPost("http://127.0.0.1:8080/testjobs1");
    try {
        rsp=httpClient.execute(httpPost);
        log.info(">> {}",rsp.getStatusLine().getStatusCode());
    } catch (Exception e) {
        log.error(e.getMessage(),e);
    }finally{
        HttpUtil.close(rsp);
    }
}

这种方案,可以实现retry,并且可以根据我的需求进行retry,如:retry count,但是就不能控制retry时间的间隔,也只好放弃了,继续寻找找到了下面这个ServiceUnavailableRetryStrategy

ServiceUnavailableRetryStrategy

可以实现,满足需求,这具有HttpRequestRetryHandler的所有有点,并且可以自定义retry时间的间隔,如下,是我定义的httpclient pool,

public static CloseableHttpClient getHttpClient() {
    ServiceUnavailableRetryStrategy serviceUnavailableRetryStrategy = new ServiceUnavailableRetryStrategy() {
        /**
         * retry逻辑
         */
        @Override
        public boolean retryRequest(HttpResponse response, int executionCount, HttpContext context) {
            if (executionCount <= 3)
                return true;
            else
                return false;
        }
        /**
         * retry间隔时间
         */
        @Override
        public long getRetryInterval() {
            return 2000;
        }
    };
    PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();
    cm.setMaxTotal(MAX_TOTAL);
    cm.setDefaultMaxPerRoute(MAX_PERROUTE);
    CloseableHttpClient httpClient = HttpClients.custom().setRetryHandler(new DefaultHttpRequestRetryHandler())
        .setConnectionManager(cm).build();
    return httpClient;
}

如下是我的测试代码

@Test
public void test6(){
    HttpPost httpPost=new HttpPost("http://127.0.0.1:8080/testjobs1");
    try {
        rsp=httpClient.execute(httpPost);
        log.info(">> {}",rsp.getStatusLine().getStatusCode());
    } catch (Exception e) {
        log.error(e.getMessage(),e);
    }finally{
        HttpUtil.close(rsp);
    }
}
标签: HttpClient
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